Assays of Ras protein exchange activity in immunoprecipitates from 3T3/hm1 cells transiently transfected with a vector reveal the role of Ras-GRF as an intermediary between G-protein betagamma subunits. These subunits are generated by muscarinic receptors and Ras, and an increase in the specific activity of Ras-GRF may easily be related to an increase in its phosphorylation state. Stimulation of the cells with carbachol provides a 50% rise in the Ras exchange activity, and provides support to the notion of a G-protein-coupled mechanism for Ras activation.

Phosphorylation of the S. cerevisiae Cdc25 in response to glucose results in its dissociation from Ras

Article Abstract:

Phosphorylation in the yeast Sacchromyces cerevisiae is enhanced by the addition of glucose to starved cells. The glucose stimulates a short-lived rise in the cyclic AMP level, which in turn produces a cascade of protein phosphorylation. This takes place on the Cdc25/Ras/adenylyl cyclase pathway, in which Cdc25 catalyzes GDP-GTP exchange on Ras. With this process Cdc25 partially relocates to the cytoplasm, which reduces its accessibility to Ras in the membrane. Commonalities between yeast and mammals give these results general significance.

Inhibition of acute lymphoblastic leukaemia by a Jak-2 inhibitor

Article Abstract:

The tyrphostin AG-490 suppresses acute lymphoblastic leukaemia cells by inactivating the Jak-2 protein tyrosine kinase (PTK). AG-490 inhibits cell growth by causing programmed cell deaths of the leukemia cells. Normal hematopoiesis is unaffected by AG-490. The Jak-2 PTK is active in leukemia cell lines and the patients of leukemia in relapse and is probably necessary for the growth of leukemia cells.